New Accounting Pronouncements (Details) - Accounting Standards Update 2016-09 [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Feb. 25, 2018	Feb. 25, 2018	Feb. 26, 2017
Recognized tax windfall benefits related to the exercise of stock-based awards	$ 6.6	$ 26.8
Reclassification of recognized tax windfall benefits related to the exercise of stock-based awards from financing activities to operating activities		26.8	$ 65.1
Reclassification of employee tax withholdings on stock-based awards from operating activities to financing activities		$ 21.4	$ 35.2

Amount of cash inflow reclassified from financing activities to operating activities for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

No definition available.

Name:	gis_ExcessTaxBenefitFromShareBasedCompensationReclassificationFromFinancingActivitiesToOperatingActivities
Namespace Prefix:	gis_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration